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I have a custom rifle built on a VZ24 (Mauser 98) action. It has a Lilja barrel. As per Sammi pressure should be @ 51000 psi. We all know the reason for this low pressure, old military rifles whos action can not handle any thing more. Using "Quickload and Nosler Reloading guide (5th. Edition) I can just reach 48000 psi (As per Quickload)and than I start blowing the web off my cases. I've been using Norma brass. I'm puzzled why this is happening. I reload this rifle as follows: I keep the bullet octive .015 off the lands.I have tried Win 760, H414 and IMR4350 each one starts to blow the web off the brass bases as soon as I start to reach aprox 48000 pounds. These loads are in the middle of Nolser loads. I should be able to reach 56000 pounds easily. Any guidance will be helpful. Howard | ||
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As one of the resident 7x57 nuts maybe I can help. First big question is how your chamber was cut, long or standard Sammi dimensions. A long throated rifle will give you more flexibility with the higher pressure loads. Your chamber the best way to figure out is do a chamber cast and sit down with the drawing spec's in front of you and a set of Micrometers. I can make some guesses but they would be just that...guesses. Next is what is your COL? This is going to get related to the chamber cast above. I am very fussy on my chambers in the 7x57, the long throat is the best setup in my experience with this round. In leau of all the trouble and bother above, some things to try, switch brass to new prodcution Winchester or Remington, even Hornady is an option. Norma brass can be soft and its thin through the web. I don't have any pressure stuff on my loads but I have chrono data. My loads were worked up in my rifles and backed off as soon as I had pressure indications, all are hot by current reloading manuals. What grain bullets are you working with, and what is your 4350 powder load? Do you have any chronograph information? I can give better advice with those data points. | |||
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STOP! You are exceeding safe pressures for one reason or another. You cant use books to figure pressure because all rifles are different. They are guides, not bibles. What are your specific loads, Brass, bullet, primer and specific charge? And are the loads that are not causing case head seperation leaving any marks on the brass or effecting primers? I expect there is either a problem with the rifle or the brass. | |||
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Maybe you have a 6.5mm barrel chambered in 7x57  | |||
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hglass Let me know your overall length, how much H414 and 4350 you're using and any other info. I've got tons of reloading info on 7x57 for 30 years and several rifles. Also first thing I'd check is your Norma cases, see if the have an Re on the case head next to the 7x57 designation, those are the really soft ones, will blow primers with normal loads, etc. If you have any of those, I'd trash them. Get a chronograph reading on your loads, I can cross that with the ones I've shot with my pressure trace system, and it'll give you a closer estimate of pressure than the Quickload. A shot not taken is always a miss | |||
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I don't have a 7x57 but your question is really a general one. Are you using a chronograph? Books & quikload are guides. You may be way over your pressure levels & a vel. reading would help you see where you have been & where you are going. When you say "blowing the web off", do you mean litterally separating the case heads? Please give some examples of your loads so we can better diagnose this one. No program or book will give you a pressure reading, just an idea. The chorno helps, but again, just a tool to use as a guide. LIFE IS NOT A SPECTATOR'S SPORT! | |||
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Sounds to me like you have an excess headspace problem. If you are experiencing case head separations, that is the most likely culprit. But there has to be enough room in the chamber for the case to be pushed forward by the firing pin, then be expanded back by expanding powder gases, for that to happen. Take a re-sized, empty case. Put four pieces of Scotch Tape over the case head, trim off the excess, and chamber the case. It should close, but should be a bit snug. If you can put over about six layers of tape on the case head, your headspace is excessive. (Each piece of Scotch tape is ~.0015" thick, and my gunsmith says anything over about .007 is undesirable.) How many times have these cases been used, and are you full length sizing them before each loading? If so, you are pushing the shoulder back with every loading, and the brass that is being extruded out the neck and being trimmed off when you re-size is coming from the area just forward of the case web, making that area the weak spot. It is also possible that your smith just chambered the barrel with excess headspace. That can be remedied by partial length sizing the brass, and staying off the shoulder. But if the separation is happening with new brass, your headspace is excessive, and from what I understand, cannot be corrected without turning a thread off the barrel and re-chambering it. | |||
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Buy a nogo guage and test. Does it chamber your reloads easily? Have you tried any factory cartridges (don't do this until you check the headspace and figure-out the problem). What sizing dies are you using and how do you adjust them? ______________________________ DT | |||
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I took a new case and put 4 strips of scotch tape on the head, I was able to close the bolt but it was tight. With six layers I was not able to close the bolt. These cases have been shot 5-6 times and I use a full length resizing die. If I back off the lands (now I set my bullet heads .015 off the lands)to .050 would that reduce the pressure spike? Should I only neck size the cases?
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It seems that your sizing your fired cases too short on the headspace for your chamber. Also your chamber may be on the long side but with the proper die set you should be ok. Even if your not FL sizing to the shell holder now dies, chambers and shell holder vary and you may need to back up that die. I have the same situation with an old Mauser thats .003" over the No Go gage. Such chambers are still serviceable. Take a fired case and FL size it with the die backed up some and try it in the rifle with the firing pin removed. Keep screwing the die in one test at a time til the bolt just closes easily. Join the NRA | |||
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Savage99 is probably correct about the maladjusted die. Just screwing them in until they hit the shellholder isn't necessary a safe practice. Think about it. The other possibility (perhaps in combination with moving the shoulder back too far) is that the the brass needs trimming. You could be crimping the bullet when chambering, thus increasing pressure. How long are the cases? ______________________________ DT | |||
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My cases are text book, 2.235 @ max and when I trimm them I bring them down to 2.225. My O.A.L. is 3.036 with Sierra "Pro Hunter"
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Your rifle is considerably shorter throated than either of mine. My 7x57 loads with 140 Sierras were 3.142 OAL at .030 off the lands. Normally a head separation is caused by oversizing, not pressure problems. I've only had it happen with belted cases before I learned to set up the dies properly and it happened after about 4-5 loadings. A chronograph will tell you if pressure is off the chart as the velocity will be too high as well. If your velocity is between 2900 and 3000 fps with 140's, 2700-2800 with 150's I'd bet it isn't a pressure problem. A shot not taken is always a miss | |||
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Use the tape on a FL sized case NOT a new one | |||
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